1. Technical Field
Illustrative embodiments described in this patent specification generally relate to a failure predictor for a fixing device included in an image forming apparatus employing an electrophotographic method, a fixing device including the failure predictor, an image forming apparatus including the fixing device, and a failure prediction system.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet of paper, etc.) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image carrier (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
Various techniques have been proposed to predict failure of the image forming apparatuses employing the electrophotographic method. One example of the technique involves obtaining a mixing ratio (absolute humidity) from temperature and humidity and uses the mixing ratio as an information amount together with output and adjusted values of a separation differential current to estimate defect rates for separation differential current regulation, a separation charger, and a transfer material by fuzzy inference. In another approach, probability of failure of a node is specified from an operating state value and a sheet conveyance time value using a Bayesian Network to extract points where failure has occurred or candidates of points where failure is likely to occur in the near future based on the probability thus specified. In yet another approach, a comprehensive index value is calculated taking into consideration operation control data of multiple types of apparatuses to determine presence or absence of irregularity in an apparatus or to predict failure of the apparatus based on the index value thus calculated.
The fixing device included in the image forming apparatus employing the electrophotographic method generally includes a pair of rotary bodies composed of a fixing member and a pressing member pressed against each other to form a fixing nip therebetween. The sheet bearing an unfixed toner image thereon is conveyed through the fixing nip so that heat and pressure are applied to the sheet. As a result, the toner image is melted and fixed onto the sheet.
Sheets having different sizes, thicknesses, or materials conveyed through the fixing nip or a separation pick that separates the sheets from the fixing member often scratch a surface of the fixing member, giving the toner image fixed onto the sheet an uneven glossiness.
In order to solve the above-described problem, the inventors of the present invention have invented a novel fixing device in which the condition of the surface of the fixing member is gauged and the surface of the fixing member is polished when a surface smoothness of the fixing member falls below a predetermined value. Specifically, a linear velocity of the fixing member is differentiated from that of the pressing member to generate slip therebetween at the fixing nip to recover the degraded surface of the fixing member.
Because the above-described fixing device having the function to recover the degraded surface of the fixing member has been newly invented, it is needless to say that a failure predictor that predicts or specifies factors for failure of such a fixing device is not yet found. None of the above-described related-art techniques is simply applicable to the newly-invented fixing device. Further, regardless of the function of recovering the degraded surface of the fixing member, a technique that can predict or specify occurrence of failure caused by degraded performance of the fixing device is not yet found. Therefore, it is necessary to provide a novel technique that can predict or specify occurrence of failure of the fixing device.